Purification of organic liquids containing acid impurities



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f 3,079,428 Fatented Feb, '26,

a r 3,679,428 'PUREICATION OFORGANIC LIQUIDS s, CONT ININGACIDIMPURITIES Massimo Baer, Longmeadow, and Mi'chael'F. Vignale, Springfield; Mass., assignors to 'Monsantp Chemical (Iompany, St. Louis; 0., a 'cnrpoiation of Delaware N Drawing. Filed ()ct.20,-1959, Ser. No. 847,472 6 Claims. (Cl. 260486) This invention relatestorinsoluble polymei'ic anionic materials. More particularly, .the invention relates tto .insolublepolymeric anionic materials which are useful as piurifying agents for removing acidic impurities from organic liquids. v,

,Because of the sensitivity of anionic polymerization systems to acidic impurities, i.e., proton donors, Which destroy or consume the growing'chaius and initiator, solvents and monomers to be employed in such polymerization systems should be substantially, free'of impurities aving apKa value lower than that of the monomers to 'be. polymerized, i.e., impurities which are more highly acid than the monomers Many materials known to be capableof reacting with the acidic impurities cannot be used to purify the solvents and monomers, because in order to be suitable as a, purifying agent in this application a material must satisfy these general requirements: (1) It must be capable of removing the acidic inipurities without contaminating the solvents and/or monomers with another impurity which'reacts with anionic initiators, and

,(2) It must be inert to the IiquidbeingJpurified, e.g., it must ib'e'incapable of initiating polymerization of the monomer being-purified. l t

I As usedvthroughout the specification, terms referring to acidity shouldjbe understoodas follows in the'sense of the definitions derived from the proton-transfer theory of acids and bases: V, t

(1) Acid-product obtained byiadding a protonto a base, a'base being any substance which, because 'of an unshared electronpair, can accept a'proton,

(2) Conjugate acid-acid related *to'apa'rticul'ar base in being the product obtained by adding a proton to that base, M

(3); pKa valuenegative logarithm of the dissociation constant of an acid. t It will be noted that, whenunderstood in this sense, the term acid is not restricted to the inorganic, carlboxylic, and, ,sulfonic compounds conventionally designated as acids, i.e., compounds having low pKa values ofup to about 10, but also embraces compounds of much higher pKa value. 7 v t O ne objectof this invention is to pr'ovide means for purifying organic liquids of acidic'impurities, i.e., impurities having a pKa value lower than that of the organic liquid, t

'Another object is to provide means for purifying organic iquids of acidic impurities without contaminating the liquids with other impurities capable of reacting with anionic polymerization initiators. V .A furtherobject is to provide'mean's for purifying organic liquids of acidic impurities without causing'reaotion of the liquid being purified. r l t The se andother objects are attained by purifying an organic liquid 7 of acidic impurities by contacting the liquid with an insoluble polymeric anionic material which isinert .to the liquid, said anionic material being an alkali metal'salh or alkaline earth metal salt of an insoluble, erossf-linkedpolymer containing a plurality ofunits capable "of reacting with an alkali metal or alkaline earth '2 metal to form an anion, the conjugate acid having a pKa valueof at least 16. The following examples are given to illustrate the invention. Parts mentioned are parts by Weight.

EXAMPLE I 's qi i it in en A suitable reaction vessel is charged with BTOQparts of water, followed by addition of. 1 partof'bentonite with agitation. The'slurry is heated to 70f C., and}.

of said an:

mixture of 50 parts of. vinyl fluorene, 4O partslof styrene,

'10 parts of divinyl benzene, and'l part of benzoyl peroxide is added thereto. The air in the-vessel is purged with nitrogen, and the pressurized vessel contents are heated at 88+90 C. for '20 hours and then-at 1l5120 C. for 12 hours. The batch is cooled anddischarged into a centrifuge where the suspension is collected andwashed .Wit hot water.. The polymer beads ,are dried in a forged dra'ftair oven for 12 hours at 110-120 C, and washed with 'LZ-dimethoxYe'thane to form substantially pure beads of cross-linked vinyl fluorene stvrene divinyl benzene (50':40:l0)terpolymer. t. t. A molar solution of sodium naphthalene in 1 ,i2:cl i methox'yethane is passed through a column containing the polymer beads inorder to replace the active hydrogen atoms of "the vinyl, fluorenefu'nits withlso dium. The effluent from the column, a solution of diliydronaphthalene and sodium naphthalenein'LZ-dimethoXYethaiie, is collected in areceiver. The 'treatment of the polymer with sodium naphthalene solution is continued until the c'onc'entration of sodium naphthalenein theefiluent solution indicates no further capacity of tthefpolymerlto react with'so'dium. The column of beads-is then washed with -LZ-climethoxyethane to remove residualsodium naphthalene and dihydronaphthalene. The product of the tr'eatment is an insoluble polymeric anionic material in which substantially, all. of the vinyl-fluorenetunits of. .the,' crosslinked vinyl fiuor ene-styrene divinyl benzene (50:40:10) ter'polymer have been converted 'to theis'odiumsjalt, The same procedureIof interpolymerizingjmonomers by suspensionpolymerization to form beads of'a crosslinked polymer and then reacting the beads with'an alkali inetalnaphthalene to form an insoluble polym'eric'anio'nic material'is used'to' prepare the following salts; v T

(1) Sodium salt of a styrene-N,N-dia1lylacrylamide (:20) copolymer in which substantially all of the active hydrogen'atoms ofthe N,N-diallylacrylamide units have been replaced with sodium, 7 p t t v, (2) :Lithium, salt of a vinyl benzyl alcohol-divinyl benzene (:10 copolymer in which substantially'all of the activehydro'gen atoms of the vinyl benzyl'alcohol units have been replaced with lithium,

(3), Lithium salt of a styrene-vinyl indene-divinyl ben- Lz'ene (6Q:30: 1O) t erpolyn1er in which'substantially all 'of the active hydrogen atoms of the Vinyl inderie units have been replaced with lithium, v v h ;(4).'Potassium salt of a styrene-vinyl fiuorenedivinyl benzene (0:30:l te1'polymer in Whichsubstantiallyall ofthe active hydrogen atoms of the vinyl fluorene units have been replaced with potassium, and

,1 (5) Potassium salt ofta p-aminostyrene-styrene-divinyl l :enzene (8"0: l0: l0)terpolymer in which substantiallyfall of the active hydrogen atoms of the p-aminostyrene units have been replaced with potassium.

EXAMPLE II Purification of Organic Liquids organic liquids are purified, using the indicated inacre res soluble polymeric anionic materials of Example I as puritying agents:

Organic liquid Purifying agent Benzene Na salt of vinyl flucrene-styrene-diviny benzene (50:40: terpclymer. 1,2-dimethoxyethane Na salt of styrene-N,N-d1allylacrylamide (80:20) copolymer. Methyl methacrylate Li salt of vinyl benzyl alcohol-divmyl benzene (90:10) copolymer. Styrene Li salt of styrene-vinyl indene-divinyl benzene (60:30:10) terpolymer. Butadiene K salt of styrene-vinyl fluorene-divmyl benzene (60:30:10) terpolymer. Isoprene K salt of p-aminostyrene-styrene-d1vmyl benzene (80:10:10) terpolymer.

In each case purification is accomplished by passing the organic liquid through a column of beads of the purifying agent, and in each case the effluent from the column is an unreacted organic liquid substantially free of acidic impurities.

EXAMPLE Demonstration of Efiectiveness of Purification through a column of beads of the sodium salt of the vinyl fluorene-styrene-divinyl benzene (50:40:10) terpolyme'r of Example I. The efiluent from the column is charged to a suitable reaction vessel, followed by the addition with agitation of the second half of the substantially pure, carefully-degassed initiator solution, an inert atmosphere being maintained in the vessel throughout the reaction. The' reaction results in substantially quantitative conversion of styrene to high molecular weight polystyrene.

The present invention relates to novel insoluble polymeric anionic materials and to their use as purifying agents for organic liquids containing acidic impurities.

The insoluble polymeric anionic materials are the alkali metal salts and alkaline earth metal salts of insoluble, cross-linked polymers containing a plurality of units capable of reacting with an alkali metal or alkaline earth metal to form an anion, the conjugate acids of said salts having pKa values of at least 16.

Exemplary of known polymers which can be reacted with alkali metals or alkaline earth metals to form the purifying agents of the invention are copolymers of vinyl toluene, vinyl isopropyl benzene, vinyl benzyl alcohol, p acetylstyrene, p-aminostyrene, vinyl pyridine, ethyleniminc, or other polymerizable compound which, as a chemically-combined unit of a polymer, contains an active hydrogen replaceable with alkali metal or alkaline earth metal, or mixtures of such compounds, with one or more cross-linking agents such as divinyl benzene, divinyl toluene, divinyl xylene, divinyl ethylbenzene, diisopropenyl benzene, trivinyl benzene, divinyl naphthalene, trivinyl naphthalene, polyvinyl anthracene, etc., and optionally with one or more other interpolymerizable monomers, e.g., vinyl ethers, styrene, etc.

Other known polymers utilizable in preparing the puritying agents of the invention are copolymers in which the cross-linking agent, as a chemically-combined unit of a polymer, contains active hydrogen replaceable with alkali metal or alkaline earth metal. Such cross-linking agents are, for example, p-diallyl benzene, diallyl melamine, N,N-diallylacrylamide, allyl silancs, and the like,

l,2-di methoxyethane, an inert atmoswhich in the course of polymerization leave residual unreacted allyl groups. These cross-linking agents are copolymerized with one or more monoethylenically-unsaturated copolymerizable monomer-s which may, if desired, also be monomers which, as a chemically-combined unit of a polymer, contain active hydrogen replaceable with alkali metal or alkaline earth metal. Alternatively, the cross-linking agent may constitute the only polymeric component capable of reacting with an alkali metal or alkaline earth metal to form an anion. 7

However, since the only requirement of the polymers with which alkali metal or alkaline earth metal is reacted to form the purifying agents of the invention is that they be insoluble, cross-linked polymers containing a plurality of units capable of reacting with alkali metal or alkaline earth metal to form'an anion and that they have a pKa value at least as high as 16, and since monomers capable of contributing such units containing active hydrogen are already well known, various other polymers utilizable in preparing the purifying agents will be obvious to those skilled in the art. The polymers usually should contain about l-40%, preferably 525%, by weight of units of the cross-linking agent and at least about 10% by weight of units capable of reacting with alkali metal or alkaline earth metal to form an anion. They can be prepared by any suitable polymerization technique, advantageously by suspension polymerization of the monomers to form polymer beads, as demonstrated in Example I, or by impregnating an inert carrier, e.g., silica gel, alumina, calcium sulfate, carbon black, diatomaceous earths, clays, etc, with the monomers and then polymerizing to form a thin coating of polymer on a large surface of the inert carrier.

The purifying agents of the invention are prepared by reacting these insoluble, cross-linked polymers with a metal of group IA .or HA of the periodic classification of the elements, i.e., with Li, Na, K, Rb, Cs, Mg, Ca, Ba, or Sr, to replace the active hydrogen atoms of the polymer with metal thus forming an insoluble polymeric anionic material. This reaction can be accomplished by contacting the polymer in any suitable manner with a solution or dispersion of the metal in an inert liquid medium or, more efficiently, by contacting the'polymer with a solution or dispersion in an inert liquid medium of an organometallic compound of the metal whose conjugate acid is weaker than that contained in the insoluble polymer. Advantageously, the polymer is reacted with the metal by contacting it with a solution of an ion-radical adduct, c.g., sodium naphthalene, in a polar solvent such as 1,2- dimethoxyethane, as demonstrated in Example I.

The treatment of the/polymer with the metal-containing composition is preferably continued until the capability of the polymer to react with the alkali metal or alkaline earth metal is exhausted in order to furnish the polymer with the maximum number of possible sites for subsequent reaction with acidic impurities contaminating the organic liquids to be purified. However, this exhaustion of the capability of the polymer to react with alkali metal or alkaline earth metal is obviously not required to make the polymeric anionic materials effective as purifying agents, particularly when the polymer contains a large number of units capable of reacting with alkali metal or alkaline earth metal. After completion of the treatment of the insoluble polymer with the alkali metal or alkaline earth metal, the polymeric anionic material is preferably washed with an inert solvent, e.g., liquid ammonia, to remove unreacted metal, metal compound, or residue of metal compound.

The insoluble polymeric anionic materials of the in vention are efiective as agents for purifying organic liquids of acidic impurities. The invention is particularly applicable to the purification of organic liquids to be employed in anionic polymerization systems, e.g., anionically-polymerizable vinylidene monomers such as styrene, vinyl toluene, 0-, m-, and p-methoxy-styrenes, butadiene,

isoprene, methyl methacrylate, etc., or solvents such as benzene, hexane, tetrahydrofuran, 1,2-dimethoxyethane, etc., but it can also be applied to the purification of any organic liquid which is contaminated by impurities having a pKa value lower than that of the liquid.

Purification of the organic liquids is accomplished by contacting the liquid with the purifying agent in any suitable manner, advantageously by passing the liquid through a. column of beads of the purifying agent, as demon strated in Examples 11 and 111. After being used to purify an organic liquid, the insoluble polymeric anionic material can be regenerated by repeating the metal treatment used in preparing the purifying agent.

Since the various organic liquids which can be purified of acidic impurities by the insoluble polymeric anionic materials of the invention have varying degrees of reactivity with anionic materials, care must be taken in the choice of a purifying agent for a particular organic liquid to insure removal of the acidic impurities without causing undesrable reaction of the liquid. The suitability of a particular insoluble polymeric anionic material as a purifying agent for organic liquids can readily be determined by routine experimentation, and in many cases this determination of the suitability of the anionic material is facilitated by the fact that the reactivity or lack of reactivity of many of the organic liquids with anionic materials of varying pKa values is already known. For greatest efiiciency in removing acidic impurities, the purifying agent should have as high a pKa value as is consistent with the requirement that it be inert to the organic liquid being purified.

The invention is particularly advantageous in that it provides novel insoluble polymeric anionic materials which, when used as purifying agents for organic liquids, enable the removal from solvents and monomers of substantially all of the acidic impurities which interfere with anionic polymerization without contaminating the solvents and monomers with other impurities which would react with anionic initiators.

It is obvious that many variations may be made in the products and processes set forth above without departing from the spirit and scope of this invention.

What is claimed is:

1. A process for purifying an organic liquid of more highly acidic impurities which comprises contacting the liquid with an insoluble polymeric anionic material which is inert to the liquid, said anionic material being a salt of a metal of the group consisting of alkali metals and alkaline earth metals with an insoluble, cross-linked polymer containing a plurality of units capable of reacting with said metal to form an anion whose conjugate acid has a pKa value at least as high as 16.

2. A process as in claim 1 wherein the organic liquid is an anionically-polymerizable vinylidene monomer.

3. A process for purifyirig methyl methacrylate of more highly acidic impurities which comprises contacting the methyl methacrylate with a lithium salt of an insoluble, cross linked vinyl benzyl alcohol-divinyl benzene co polymer.

4. A process for purifying styrene of more highly acidic impurities which comprises contacting the styrene with a sodium salt of an insoluble, cross-linked vinyl fiuorenestyrene-divinyl benzene terpolymer.

5. A process for purifying butadiene of more highly acidic impurities which comprises contacting the butadiene with a potassium salt of an insoluble, cross-linked styrenevinyl fluorene-divinyl benzene terpolymer.

6. A process for purifying isoprene of more highly acidic impurities which comprises contacting the isoprene with a potassium salt of an insoluble, cross-linked p aminostyrene-styrene-divinyl benzene terpolymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,387 Basdekis et al. Sept. 2, 1952 2,687,383 DAlelio Aug. 24, 1954 2,704,770 Anspon Mar. 22, 1955 2,891,916 Hwa June 23, 1959 OTHER REFERENCES Ion Exchangers in Organic and Biochemistry (1957), pages -156, pages 139, 140, 143, 147, -151 particularly relied upon; Interscience Publishers, Inc., New York. 

1. A PROCESS FOR PURIFYING AN ORGANIC LIQUID OF MORE HIGHLY ACIDIC IMPURITIES WHICH COMPRISES CONTACTING THE LIQUID WITH AN INSOLUBLE POLYMERIC ANIONIC MATERIAL WHICH IS INERT TO THE LIQUID, SAID ANIONIC MATERIAL BEING A SALT OF A METAL OF THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS WITH AN INSOLUBLE, CROSS-LINKED POLYMER CONTAINING A PLURALITY OF UNITS CAPABLE OF REACTING WITH SAID METAL TO FORM AN ANNION WHOSE CONJUGATE ACID HAS A PKA VALUE AT LEAST AS HIGH AS
 16. 